3 Easy Tools for Spotting the ISS

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What’s the size of a football field and shines as bright as Jupiter? The International Space Station!

If you have spent any amount of time looking up at the night sky, you have almost certainly seen satellites making their way across the star field. Most of these are relatively dim, but some occasionally flare brighter than any of the visible planets.

Not surprisingly the easiest man made satellite to spot is the largest, and in a relatively low orbit, which can make it a brilliant sight! Here are a few handy tools for spotting the ISS from just about anywhere in the world.

NASA ISS Email Alerts

NASA provides an automated system that can send you and email or text message about 12 hours before an ISS flyover. They will only message you for what are considered good ISS passes, meaning the station is relatively high in the sky and bright. Note that they don’t take local weather conditions into account. Here’s an example of the message format:

Time: Wed Feb 20 7:25 PM, Visible: 2 min, Max Height: 72 degrees, 
Appears: WNW, Disappears: ENE

ISS AstroViewer

This site is a great compliment to the NASA alerts, and can show you information about a predicted ISS pass, including the visual magnitude (how bright it will be) and exactly when during the pass it will be visible (sun-lit). Just type in your zip code on your first visit, and it will remember your location.

Note: The visual magnitude scale is an odd beast where negative values are brighter than positive values. The value of 0 is equal to the brightest star (Vega). A value of -3 is about the same brightness as Jupiter.

Star Walk

In addition to the above two resources, being able to see exactly where in the sky the ISS will pass can be helpful in locating it before it’s gone. Star Walk and similar apps are handy for this. You can set the clock in Star Walk ahead to the ISS sighting time, and follow where the station will be in the sky relative to the constellations and other bright markers.

So check your local forecast, and the next time you have a clear night, check and see if the ISS will be passing over. It adds a little more fun to your stargazing.